Tubulin is an essential eukaryotic protein that plays critical roles in cell division and is an established target of anticancer drug development. Combretastatins (S1), chalcones (S2), podophyllotoxins (S3) and Colchicines (S4) are the notable examples of compounds that inhibit microtubule assembly by binding to tubulin. Many mechanisms of action have been identified, including the inhibition of tubulin assembly, inhibition of angiogenesis, induction of apoptosis, anti-estrogenic activity and reversal of multidrug resistance or a combination of these mechanisms (Ducki, S. The development of chalcones as promising anticancer agents. Invest. New Drugs. 2007, 10, 42-46; Boumendjel, A., Boccard, J., Carrupt, P.-A., Nicolle, E., Blanc, M., Geze, A., Choisnard, L., Wouessidjewe, D., Matera, E.-L. and Dumontet, C. Antimitotic and Antiproliferative activities of chalcones. J. Med. Chem. 2008, 51, 2307-2310; Sharma, N., Mohanakrishnan, D., Shard, A., Sharma, A., Saima, Sinha, A. K. and Sahal, D. Stilbene-chalcone hybrids: design, synthesis, and evaluation as a new class of antimalarial scaffolds that trigger cell death through stage specific apoptosis. J. Med. Chem. 2012, 55, 297-311). A more recent reevaluation of this type of compounds by NCI against human tumor cell lines reconfirmed that, like colchicine, they are effective inhibitors of tubulin polymerization. Pyrazole (NSC-45410) is a low molecular weight, heterocyclic compound which has been considered for reevaluation in the clinic as a potential cytotoxic agent. (O'Dwyer. P J, King S A, Plowman J, Grieshaber C K, Hoth D F, Leyland-Jones B. Pyrazole: preclinical reassessment. Invest New Drugs; 1988, 6, 305-310; Sidique, S., Ardecky, R., Su, Y., Narisawa, S., Brown, B., Millan, J. L., Sergienko, E. and Cosford, N. D., Design and synthesis of pyrazole as potent and selective inhibitors of tissue-nonspecific alkaline phosphatase (TNAP). Bioorg. Med. Chem. Lett. 2009, 19, 222-225). Biochemical mechanistic studies performed with dihydropyridopyrazole (S3) compounds showed that these molecules inhibit in vitro tubulin polymerization and disrupt the formation of mitotic spindles in dividing cells at low nanomolar concentrations, in a manner similar to podophyllotoxin itself (Magedov, I. V., Frolova, L., Manpadi, M., Bhoga, U. D., Tang, H., Evdokimov, N. M., George, O., Georgiou, K. H., Renner, S., Getlik, M., Kinnibrugh, T. L., Fernandes, M. A., van Slambrouck, S., Steelant, W. F. A., Shuster, C. B., Rogelj, S., van Otterlo, W. A. L. and Kornienko, A. Anticancer properties of an important drug lead podophyllotoxin can be efficiently mimicked by diverse heterocyclic scaffolds accessible via one-step synthesis. J. Med. Chem. 2011, 54, 4234-4246). The microtubules possesses three sites for ligand binding—the vinca domain, colchicine domain and taxol domain. However, occurrence of peripheral neuropathy, high systemic toxicity and drug resistance are major limitations in the development of antimicrotubule agents as drugs (F. Pellegrini, D. R. Budman, Tubulin function, action of antitubulin drugs, and new drug development. Cancer. Invest. 2005, 23, 264-273). The unique feature of microtubule-binding agents, in contrast to other categories of anticancer drugs, is their incredible structural complexity and diversity, which provides many possibilities for new scaffold design. In recent years, combination chemotherapy with agents possessing different mechanisms of action is one of the methods, that is being adopted to treat cancer. Therefore, hybrid compounds like pyrazolochalcones described in the present invention that contain pyrazole as well as chalcone pharmacophores with different mode of action could be beneficial for the treatment of cancer.
